<div class="refentry"><a id="glLinkProgram"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glLinkProgram — link a program object</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glLinkProgram</strong>(</code></td><td>GLuint <var class="pdparam">program</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>program</code></em></span></dt><dd><p>Specifies the handle of the program object to be linked.</p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p><code class="function">glLinkProgram</code> links the program
	object specified by <em class="parameter"><code>program</code></em>. A shader object
        of type <code class="constant">GL_VERTEX_SHADER</code> attached to
        <em class="parameter"><code>program</code></em> is used to
	create an executable that will run on the programmable vertex
	processor. A shader object of type <code class="constant">GL_FRAGMENT_SHADER</code>
        attached to <em class="parameter"><code>program</code></em> is used to create an
	executable that will run on the programmable fragment
	processor.</p><p>The status of the link operation will be stored as part of
	the program object's state. This value will be set to
	<code class="constant">GL_TRUE</code> if the program object was linked
	without errors and is ready for use, and
	<code class="constant">GL_FALSE</code> otherwise. It can be queried by
	calling
	<a class="citerefentry" href="glGetProgramiv"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>
	with arguments <em class="parameter"><code>program</code></em> and
	<code class="constant">GL_LINK_STATUS</code>.</p><p>As a result of a successful link operation, all active
	user-defined uniform variables belonging to
	<em class="parameter"><code>program</code></em> will be initialized to 0, and
	each of the program object's active uniform variables will be
	assigned a location that can be queried by calling
	<a class="citerefentry" href="glGetUniformLocation"><span class="citerefentry"><span class="refentrytitle">glGetUniformLocation</span></span></a>.
	Also, any active user-defined attribute variables that have not
	been bound to a generic vertex attribute index will be bound to
	one at this time.</p><p>Linking of a program object can fail for a number of
	reasons as specified in the <span class="emphasis"><em>OpenGL ES Shading Language
	Specification</em></span>. The following lists some of the
	conditions that will cause a link error.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A vertex shader and a fragment shader are not both
                present in the program object.</p></li><li class="listitem"><p>The number of active attribute variables supported
		by the implementation has been exceeded.</p></li><li class="listitem"><p>The storage limit for uniform variables has been
		exceeded.</p></li><li class="listitem"><p>The number of active uniform variables supported
		by the implementation has been exceeded.</p></li><li class="listitem"><p>The <code class="function">main</code> function is missing
		for the vertex shader or the fragment shader.</p></li><li class="listitem"><p>A varying variable actually used in the fragment
		shader is not declared in the same way (or is not
		declared at all) in the vertex shader.</p></li><li class="listitem"><p>A reference to a function or variable name is
		unresolved.</p></li><li class="listitem"><p>A shared global is declared with two different
		types or two different initial values.</p></li><li class="listitem"><p>One or more of the attached shader objects has not
		been successfully compiled (via <a class="citerefentry" href="glCompileShader"><span class="citerefentry"><span class="refentrytitle">glCompileShader</span></span></a>)
                or loaded with a pre-compiled shader binary (via <a class="citerefentry" href="glShaderBinary"><span class="citerefentry"><span class="refentrytitle">glShaderBinary</span></span></a>).</p></li><li class="listitem"><p>Binding a generic attribute matrix caused some
		rows of the matrix to fall outside the allowed maximum
		of <code class="constant">GL_MAX_VERTEX_ATTRIBS</code>.</p></li><li class="listitem"><p>Not enough contiguous vertex attribute slots could
		be found to bind attribute matrices.</p></li></ul></div><p>When a program object has been successfully linked, the
	program object can be made part of current state by calling
	<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>.
	Whether or not the link operation was successful, the program
	object's information log will be overwritten. The information
	log can be retrieved by calling
	<a class="citerefentry" href="glGetProgramInfoLog"><span class="citerefentry"><span class="refentrytitle">glGetProgramInfoLog</span></span></a>.</p><p><code class="function">glLinkProgram</code> will also install the
	generated executables as part of the current rendering state if
	the link operation was successful and the specified program
	object is already currently in use as a result of a previous
	call to
	<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>.
	If the program object currently in use is relinked
	unsuccessfully, its link status will be set to
	<code class="constant">GL_FALSE</code> , but the executables and
	associated state will remain part of the current state until a
	subsequent call to <code class="function">glUseProgram</code> removes it
	from use. After it is removed from use, it cannot be made part
	of current state until it has been successfully relinked.</p><p>The program object's information log is updated and the
	program is generated at the time of the link operation. After
	the link operation, applications are free to modify attached
	shader objects, compile attached shader objects, detach shader
	objects, delete shader objects, and attach additional shader
	objects. None of these operations affects the information log or
	the program that is part of the program object.</p></div><div class="refsect1"><a id="notes"></a><h2>Notes</h2><p>If the link operation is unsuccessful, any information about a previous link operation on <em class="parameter"><code>program</code></em>
	is lost (i.e., a failed link does not restore the old state of <em class="parameter"><code>program</code></em>).
	Certain information can still be retrieved from <em class="parameter"><code>program</code></em>
	even after an unsuccessful link operation. See for instance <a class="citerefentry" href="glGetActiveAttrib"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>
	and <a class="citerefentry" href="glGetActiveUniform"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniform</span></span></a>.</p></div><div class="refsect1"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_VALUE</code>
	is generated if <em class="parameter"><code>program</code></em>
	is not a value generated by OpenGL.</p><p><code class="constant">GL_INVALID_OPERATION</code>
	is generated if <em class="parameter"><code>program</code></em>
	is not a program object.</p></div><div class="refsect1"><a id="associatedgets"></a><h2>Associated Gets</h2><p><a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>
	with the argument <code class="constant">GL_CURRENT_PROGRAM</code></p><p><a class="citerefentry" href="glGetActiveAttrib"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>
	with argument <em class="parameter"><code>program</code></em>
	and the index of an active attribute variable</p><p><a class="citerefentry" href="glGetActiveUniform"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniform</span></span></a>
	with argument <em class="parameter"><code>program</code></em>
	and the index of an active uniform variable<em class="parameter"><code></code></em></p><p><a class="citerefentry" href="glGetAttachedShaders"><span class="citerefentry"><span class="refentrytitle">glGetAttachedShaders</span></span></a>
	with argument <em class="parameter"><code>program</code></em></p><p><a class="citerefentry" href="glGetAttribLocation"><span class="citerefentry"><span class="refentrytitle">glGetAttribLocation</span></span></a>
	with argument <em class="parameter"><code>program</code></em>
	and an attribute variable name</p><p><a class="citerefentry" href="glGetProgramiv"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>
	with arguments <em class="parameter"><code>program</code></em>
	and <code class="constant">GL_LINK_STATUS</code></p><p><a class="citerefentry" href="glGetProgramInfoLog"><span class="citerefentry"><span class="refentrytitle">glGetProgramInfoLog</span></span></a>
	with argument <em class="parameter"><code>program</code></em></p><p><a class="citerefentry" href="glGetUniform"><span class="citerefentry"><span class="refentrytitle">glGetUniform</span></span></a>
	with argument <em class="parameter"><code>program</code></em>
	and a uniform variable location</p><p><a class="citerefentry" href="glGetUniformLocation"><span class="citerefentry"><span class="refentrytitle">glGetUniformLocation</span></span></a>
	with argument <em class="parameter"><code>program</code></em>
	and a uniform variable name</p><p><a class="citerefentry" href="glIsProgram"><span class="citerefentry"><span class="refentrytitle">glIsProgram</span></span></a></p></div>
        {$pipelinestall}{$examples}
        <div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p><a class="citerefentry" href="glAttachShader"><span class="citerefentry"><span class="refentrytitle">glAttachShader</span></span></a>,
	<a class="citerefentry" href="glBindAttribLocation"><span class="citerefentry"><span class="refentrytitle">glBindAttribLocation</span></span></a>,
	<a class="citerefentry" href="glCompileShader"><span class="citerefentry"><span class="refentrytitle">glCompileShader</span></span></a>,
	<a class="citerefentry" href="glShaderBinary"><span class="citerefentry"><span class="refentrytitle">glShaderBinary</span></span></a>,
	<a class="citerefentry" href="glCreateProgram"><span class="citerefentry"><span class="refentrytitle">glCreateProgram</span></span></a>,
	<a class="citerefentry" href="glDeleteProgram"><span class="citerefentry"><span class="refentrytitle">glDeleteProgram</span></span></a>,
	<a class="citerefentry" href="glDetachShader"><span class="citerefentry"><span class="refentrytitle">glDetachShader</span></span></a>,
	<a class="citerefentry" href="glUniform"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a>,
	<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>,
	<a class="citerefentry" href="glValidateProgram"><span class="citerefentry"><span class="refentrytitle">glValidateProgram</span></span></a></p></div><div class="refsect1"><div id="Copyright"><h2>Copyright</h2><p>
            Copyright © 2003-2005 3Dlabs Inc. Ltd.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="ulink" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.
        </p></div></div></div>
